| |
44.
Weight/Weightlessness (Phil Physiker contrasts mg with and without a support force.) End Question: If you were in a freely-falling elevator and you dropped a pencil, it would hover in front of you. Is there a force of gravity acting on the pencil? Defend your answer. |
| |
45. Gravity (Paul shows how the equation for gravity is a guide to thinking.) End Question: Pretend you’re in a spaceship that passes a giant star and you feel its gravitational pull. Then the star collapses to become a black hole. How, if at all, will your gravitational pull to the black hole compare? |
| |
46. Gravity Inside
Earth (Application of the gravitational equation to Earth’s interior is treated.) End Question: In a cavity at Earth’s center, do you experience the gravitational pull of the Sun? |
| |
47. Tunnel Through
Earth (Paul considers a tunnel bored through Earth and your motion if you were to fall into it.) End Question: When you whiz past the center of the tunnel through Earth, you have maximum speed. How does this speed compare with the constant speed of the satellite in close circular orbit? Think about that. |
| |
48. Ocean Tides (Paul explains how the Moon, and also the Sun, cause ocean tides.) End Question: Suppose you go to the beach to dig clams at the time of an extra-low tide. Is it reasonable to assume that in about six hours the tide that follows will be extra high? |